title: Prevalence of multimorbidity according to the deprivation level among the elderly in the Basque Country.
abstract: BACKGROUND
  Multimorbidity is clearly a major challenge for healthcare systems. However, currently, its magnitude and impact on healthcare expenditures is still not well known. The objective of this paper is to present an overview of the prevalence of multimorbidity by deprivation level in the elderly population of the Basque Country.
  
  
  METHODS
  We conducted a cross-sectional analysis that included all the inhabitants of the Basque Country aged 65 years and over (N = 452,698). This was based on data from primary care electronic medical records, hospital admissions, and outpatient care databases, for a 4-year period. The health problems of the patients were identified from their diagnoses and prescriptions. Multimorbidity was defined as the presence of two or more chronic diseases out of a list of 47 of the most important and common chronic conditions consistent with the literature. In addition, we explored socio-economic and demographic variables such as age, sex, and deprivation level.
  
  
  RESULTS
  Multimorbidity was found in 66.13% of the population aged 65 and over and increases with age until 80 years. The prevalence of multimorbidity was higher in deprived (69.94%) than better-off (60.22%) areas. This pattern of differences between the most and least disadvantaged areas was observed in all age groups and more marked in female (70.96-59.78%) than in male (68.54-60.86%) populations. In almost all diseases studied (43 out of 47), 90% of patients had been diagnosed with at least one other illness. It was also frequent the coexistence of mental and physical health problems in the same person and the presence of multiple physical diseases is higher in patients with mental disease than in the rest of population (74.97% vs. 58.14%).
  
  
  CONCLUSIONS
  Multimorbidity is very common among people over 65 years old in the Basque Country, particularly in unfavourable socioeconomic environments. Given the ageing population, multimorbidity and its consequences should be taken into account in healthcare policy, organization of care and medical research. Administrative health databases are readily available sources of a range of information that can be useful for such purposes.
authors.affiliation: O+berri, Basque Institute for Healthcare Innovation, Plaza Asua 1, 48150 Sondika, Spain. jon.orueta@osakidetza.net.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Orueta
authors.forename: Roberto
authors.initials: R
authors.lastname: Nuño-Solinís
authors.forename: Arturo
authors.initials: A
authors.lastname: García-Alvarez
authors.forename: Edurne
authors.initials: E
authors.lastname: Alonso-Morán
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease / Q000191:economics / Q000453:epidemiology*; D015897:Comorbidity; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D003695:Delivery of Health Care / Q000191:economics; D005260:Female; D005102:Health Expenditures / Q000639:trends*; D054625:Healthcare Disparities; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D011204:Poverty Areas; D015995:Prevalence; D013030:Spain / Q000453:epidemiology